Field of the Invention
The present invention generally relates to a sprocket. In particular, the present invention relates to a bicycle sprocket engageable with a chain having rollers.
Background Information
In a bicycle provided with a plurality of rear sprockets, speed change is performed by using a rear derailleur. When a rider on such a bicycle travels on a rough terrain, irregularities on the terrain cause the chain guide of the rear derailleur to vibrate like a pendulum, which changes the tension acting on the chain. It is preferable that a change in the tension acting on the chain is unlikely to result in disengagement of the chain from the front-side sprocket.
US 2013/0139642A1 discloses a sprocket having a plurality of first teeth and the same number of second teeth longer than the first teeth in the direction of the axis of rotation of the sprocket, that is, thicker than the first teeth with the first and second teeth alternately arranged. In this configuration, the first teeth engage with narrow-inner-width inner link plates of the chain, and the second teeth engage with wide-inner-width inner link plates of the chain, resulting in an increased chain holding force, whereby the chain is unlikely to disengage from the sprocket during travel on a rough road. Further, in the sprocket of the related art, a side surface on the upstream side in the direction in which the sprocket is driven and rotated, that is, a non-drive side surface with which the rollers of the chain do not come into contact has a shape that protrudes in the circumferential direction. The shape further increases the chain holding force.